Chemical amplification type positive photoresist composition and resist pattern forming method

ABSTRACT

The present invention provides a chemical amplification type positive photoresist composition which is excellent in storage stability as a resist solution in a bottle A novolak resin or a hydroxystyrenic resin is reacted with a crosslinking agent to give a slightly alkali-soluble or alkali-insoluble resin having such a property that solubility in an aqueous alkali solution is enhanced in the presence of an acid, which is then dissolved in an organic solvent, together with (B) a compound generating an acid under irradiation with radiation to obtain a chemical amplification type positive photoresist composition wherein the content of an acid component is 10 ppm or less.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/522,036, filed Jan. 19, 2005, which is the U.S. National Phase under35 U.S.C. 371 of International Application No. PCT/JP2004/007139, filedMay 19, 2004, which claims priority to Japanese Patent Application No.2003-141805 filed on May 20, 2003, and Japanese Patent Application No.2003-426503 filed on Dec. 24, 2003, the disclosure of which isincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel chemical amplification typepositive photoresist composition and relates to a method for formationof a resist pattern.

2. Description of the Related Art

In the fields of the production of semiconductor devices, liquid crystaldisplays, printing plates, bumps and magnetic heads, for example, therehave hitherto been used a photoresist compositions for g-rays, h-raysand i-rays, comprising an alkali soluble resin and a quinonediazidogroup-containing compound (photoactive compound: PAC) as a maincomponent; and chemical amplification type photoresist compositions forradiation such as i-rays, KrF, ArF and electron beam, comprising an aciddissociable group-containing compound (resin) and a photo acid generator(PAG) as a main component.

Examples of the chemical amplification type photoresist compositioninclude those described in the following Patent Documents 1 to 3.

Patent Document 1 describes a composition comprising a linear polymerhaving an acid component and a hydroxyl group, PAG and a compound havingat least two specific enol ether groups, the linear polymer and thespecific compound being crosslinked by heating.

Patent Document 2 describes a composition comprising a linear polymerhaving an acid group, PAG and a compound having at least two specificenol ether groups, the linear polymer and the specific compound beingcrosslinked by heating.

Patent Document 3 describes a composition comprising a partiallycrosslinked polymer, which is obtained by reacting a hydroxylgroup-containing polymer with polyvinyl ether in the presence of an acidcatalyst, and PAG.

-   -   (Patent Document 1) Japanese Patent Application, First        Publication No. Hei 6-148889    -   (Patent Document 2) Japanese Patent Application, First        Publication No. Hei 6-230574    -   (Patent Document 3) Published Japanese Translation No.        2002-529552 of the PCT Application.

Recently, the integration degree of semiconductor devices has increasedmore and more.

Various proposals have hitherto been made on chemical amplification typeresists which contribute to improvement in integration degree ofsemiconductor devices.

In the following Patent Document 4, there is described a two-componentresist comprising a base material resin wherein hydrogen of hydroxylgroups of polyhydroxystyrene having high transparency to a KrF excimerlaser beam is substituted with an acid dissociable alkali dissolutioninhibiting group, for example, tertiary alkyloxycarbonyl group such ast-boc (tert-butoxycarbonyl) group or acetal group such as 1-ethoxyethylgroup, and a photo acid generator as a main component.

A summary of the principle of the resist pattern formation in the resistproposed in Patent Document 4 is as follows. That is, since the basematerial resin has an alkali dissolution inhibiting group such as t-bocgroup, alkali solubility is inferior to polyhydroxystyrene having not-boc group. When such a resin is mixed with a photo acid generator andthe mixture is selectively exposed, the t-boc group is dissociated by anaction of an acid generated from a photo acid generator at the exposedarea to produce polyhydroxystyrene, and thus the resin becomes alkalisoluble.

-   -   (Patent Document 4) Japanese Patent Application, First        Publication No. Hei 4-211258    -   (Patent Document 5) Japanese Patent Application, First        Publication No. Hei 10-268508    -   (Patent Document 6) Japanese Patent Application, First        Publication No. 2003-167357

DISCLOSURE OF THE INVENTION

However, the compositions described in Patent Documents 1 and 2 have aproblem in that they are inferior in storage stability as a resistsolution in a bottle.

Also, the composition described in Patent Document 3 has the followingproblems. That is, acid catalyst used to prepare a polymer remains inthe resist and the composition is inferior in storage stability as aresist solution in a bottle after preparing a resist.

In a first aspect, an object of the present invention is to achieve theobject (first object).

Poor storage stability as a resist solution in a bottle refers to poorstorage stability after preparing a resist solution, and mainly refersto deterioration of properties such as sensitivity.

According to the technique described in Patent Document 4, regardingalkali solubility of a base material resin upon selective exposure,original alkali solubility of polyhydroxystyrene is recovered bydissociation of a t-boc group due to exposure, and more superior alkalisolubility can not be achieved. Therefore, it is insufficient inresolution. The use of an alkali dissolution inhibiting group is likelyto cause defects in the case of alkali development.

In Patent Document 5, there is proposed a resist material made of aresin prepared by preliminarily crosslinking a resin comprising ahydroxystyrene unit and a cyclohexanol unit with an ether group.However, the resist material is insufficient because a problem such asdefects arises.

Defects refers to scum and general defects of a resist pattern, whichare detected when observed from right above the developed resistpattern, using a surface defect detection equipment (trade name: “KLA”)manufactured by KLA-TENCOR CORPORATION.

In Patent Document 6, there is proposed a photoresist compositioncomprising a resin wherein some of the hydrogen atoms of hydroxyl groupsof hydroxystyrene are protected with an alkali dissolution inhibitinggroup such as an acetal group, a photo acid generator and a crosslinkingpolyvinyl ether compound, and the resin and the polyvinyl ether compoundare crosslinked by prebaking and patterning is conducted by subjectingto exposure, PEB (post exposure bake) and development. Since the alkalidissolution inhibiting group is introduced into the resin, the resistcomposition is insufficient because a problem such as defects arise.

Thus, the second object of the present invention is to provide apositive resist composition and resist pattern forming method, which canimprove resolution and reduce defects.

The present inventors have intensively researched and found thefollowing means for achieving the above first object.

The chemical amplification type positive photoresist composition of thefirst aspect (first example) is a chemical amplification type positivephotoresist composition (hereinafter referred to as a resistcomposition, sometimes) prepared by dissolving:

(A) a slightly alkali-soluble or alkali-insoluble novolak resin having aproperty that solubility in an aqueous alkali solution is enhanced inthe presence of an acid, comprising either or both of a constituent unit(al) represented by the following general formula (I):

wherein R¹ represents either an alkylene group having 1 to 10 carbonatoms which may have a substituent or a group represented by thefollowing general formula (II):

(wherein R⁴ represents an alkylene group having 1 to 10 carbon atomswhich may have a substituent and m represents 0 or 1), the alkylenegroup may have an oxygen bond (ether bond) in the main chain, R² and R³each independently represents a hydrogen atom or an alkyl group having 1to 3 carbon atoms, and n represents an integer of 1 to 3, and anintermolecular crosslinked moiety (a2) represented by the followinggeneral formula (III):

wherein R¹ represents either an alkylene group having 1 to 10 carbonatoms which may have a substituent or a group represented by the abovegeneral formula (II) (wherein R⁴ represents an alkylene group having 1to 10 carbon atoms which may have a substituent and m represents 0 or1), the alkylene group may have an oxygen bond (ether bond) in the mainchain, R² and R³ each independently represents hydrogen atom or alkylgroup having 1 to 3 carbon atoms, and n represents an integer of 1 to 3;and

(B) a compound generating an acid under irradiation with radiation, inan organic solvent (hereinafter sometimes referred to as an acidgenerator or a photo acid generator), wherein the content of an acidcomponent is 10 ppm or less.

Another chemical amplification type positive photoresist composition ofthe first aspect (second example) is a chemical amplification typepositive photoresist composition prepared by dissolving:

(A′) an alkali-slightly soluble or alkali-insoluble polyhydroxystyrenicresin having a property that solubility in an aqueous alkali solution isenhanced in the presence of an acid, comprising either or both of aconstituent unit (a′1) represented by the following general formula(IV):

wherein R¹ represents either an alkylene group having 1 to 10 carbonatoms which may have a substituent or a group represented by the abovegeneral formula (II) (wherein R⁴ represents an alkylene group having 1to 10 carbon atoms which may have a substituent and m represents 0 or1), the alkylene group may have an oxygen bond (ether bond) in the mainchain, and an intermolecular crosslinked moiety (a′2) represented by thefollowing general formula (V):

wherein R¹ represents either an alkylene group having 1 to 10 carbonatoms which may have a substituent or a group represented by the abovegeneral formula (II) (wherein R⁴ represents an alkylene group having 1to 10 carbon atoms which may have a substituent and m represents 0 or1), the alkylene group may have an oxygen bond (ether bond) in the mainchain; and

(B) a compound generating an acid under irradiation with radiation, inan organic solvent, wherein the content of an acid component is 10 ppmor less.

Still another chemical amplification type positive photoresistcomposition of the first aspect (third example) is a chemicalamplification type positive photoresist composition prepared bydissolving:

(A″) a slightly alkali-soluble or alkali-insoluble polyhydroxystyrenicresin having a property that solubility in an aqueous alkali solution isenhanced in the presence of an acid, comprising either or both of aconstituent unit (a′1) represented by the above general formula (IV),and an intermolecular crosslinked moiety (a′2) represented by the abovegeneral formula (V), and a styrenic constituent unit; and (B) a compoundgenerating an acid under irradiation with radiation, in an organicsolvent.

The method for synthesis of the above component (A) comprises reacting anovolak resin with a crosslinking agent represented by the followinggeneral formula (VI):H₂C═CH—O—R¹—O—CH═CH₂   (VI)wherein R¹ represents either an alkylene group having 1 to 10 carbonatoms which may have a substituent or a group represented by the abovegeneral formula (II) (wherein R⁴ represents an alkylene group having 1to 10 carbon atoms which may have a substituent and m represents 0 or 1,and the alkylene group may have an oxygen bond (ether bond) in the mainchain, in the substantial absence of an acid catalyst.

The method for synthesis of the above component (A′) comprises reactinga hydroxystyrenic resin with the crosslinking agent represented by theabove general formula (VI) in the presence of an acid catalyst.

A method for synthesis of the above component (A″) comprises reacting ahydroxystyrenic resin with the crosslinking agent represented by theabove general formula (VI) in the presence of an acid catalyst.

The method for formation of a resist pattern of the first aspect is amethod for formation of a resist pattern of a thick-filmphotolithography process, which comprises forming a resist film having athickness of 2 to 7 μm made of the chemical amplification type positiveresist composition of the first aspect (first to third example) on asubstrate, and subjecting to selective exposure, PEB (post exposurebake) treatment and development.

The constituent unit means a unit derived from the respective monomersas raw materials of a polymer in the polymer.

To achieve the second object, the following composition was employed inthe second aspect of the present invention.

The chemical amplification type positive photoresist composition of thesecond aspect is a chemical amplification type positive photoresistcomposition (hereinafter sometimes referred to as a “two-componentchemical amplification type positive photoresist composition”)comprising (A2) a resin made of a reaction product of (A1) an alkalisoluble resin and (C1) a crosslinking polyvinyl ether compound whereinalkali solubility is enhanced by an action of an acid, and (B1) a photoacid generator generating acid under irradiation with radiation, wherein

the component (A1) comprises a unit (a1′) derived from(α-methyl)hydroxystyrene represented by the following general formula(I′):

wherein R represents a hydrogen atom or a methyl group and 1 representsan integer of 1 to 3, and an alkali-insoluble unit (a2′) having no aciddissociable dissolution inhibiting group, and wherein a dissolution rateto an aqueous 2.38 wt % solution of the component (A1) in TMAH(tetramethylammonium hydroxide) is from 10 to 100 nm/second.

The resist pattern forming method of the second aspect comprisesapplying the chemical amplification type positive photoresistcomposition of the present invention on a substrate, and subjecting toprebaking, selective exposure, PEB (post exposure bake) and alkalidevelopment to form a resist pattern.

In the first aspect of the present invention, a chemical amplificationtype positive photoresist composition which is excellent in storagestability as a resist solution in a bottle is obtained.

In the second aspect of the present invention, an improvement inresolution and reduction of defects can be realized.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred aspects of the present invention will now be described. Thepresent invention is not limited to the following aspects andconstituent elements of these aspects may be appropriately combined.

First Aspect

Component (A)

Chemical Amplification Type Positive Photoresist Composition

The component (A) is a slightly alkali-soluble or alkali-insolublenovolak resin which comprises either or both of a constituent unit (a1)represented by the general formula (I) and an intermolecular crosslinkedmoiety (a2) represented by the general formula (II), and also has aproperty that solubility in an aqueous alkali solution is enhanced inthe presence of an acid.

The component (A) is preferably obtained by reacting a novolak resinwith a crosslinking agent represented by the general formula (VI) in thesubstantial absence of an acid catalyst. The contents of constituentunit (a1) to the intermolecular crosslinked moiety (a2) in the component(A) vary depending on the reaction conditions and are not specificallylimited, and both are commonly included.

When the crosslinking agent is preliminarily linked with hydroxyl groupsof the novolak resin, changes in a resist coating solution (composition)over time are suppressed and thus a resist material with less change insensitivity is obtained. When the resist material is applied on asubstrate and is then heated, phenolic hydroxyl groups in the side chainof the component (A) react with a terminal vinyl group of theconstituent unit (a1) to form a crosslinked structure. Consequently, theresist coating film becomes slightly soluble in an alkali developersolution such as aqueous alkaline solution used in resist patternformation. When an acid generated from the component (B) due to exposurereacts with the component (A) having a crosslinked structure, thecrosslinked structure is cleaved and solubility of the component (A) inan aqueous alkali solution is enhanced.

Novolak Resin

The novolak resin to be used is not specifically limited as long as itis commonly used in the resist composition and examples thereof includethose obtained by condensing at least one aromatic hydroxy compound suchas phenol, cresol, xylenol, trimethylphenol, catechol, resorcinol orhydroquinone with aldehydes and/or ketones in the presence of an acidiccatalyst.

Aldehydes and ketones are not specifically limited. Examples ofpreferable aldehydes include formaldehyde, paraformaldehyde,propionealdehyde, salicylaldehyde and crotonaldehyde, and examples ofpreferable ketones include acetone, methyl ethyl ketone and diethylketone.

Examples of the acid catalyst include oxalic acid, p-toluenesulfonicacid and acetic acid. It is preferred to use oxalic acid because it isinexpensive and readily available.

As the aromatic hydroxy compound, at least one of phenol, xylenol(including any isomer) and cresol (including o-, m- and p-isomers) maybe used. It is preferred to use m-cresol alone or a mixture ofm-cresol/p-cresol in a molar ratio of 30/70 to 50/50 because theresulting resist composition is excellent in general properties such assensitivity, resolution, and pattern shape.

Aldehydes are preferably those synthesized from formalin and bulkyaldehyde in view of an improvement in heat resistance and an increase insensitivity. Examples of the bulky aldehyde include salicylaldehyde,propionealdehyde and crotonaldehyde. The ratio of formalin to bulkyaldehyde is preferably from 1/0.1 to 1/0.6 (molar ratio), andparticularly preferably from 1/0.2 to 1/0.5 (molar ratio), in view ofsuperior effects in improving heat resistance.

Therefore, combinations of preferable aromatic hydroxy compounds andpreferable aldehydes are particularly preferable.

The weight-average molecular weight as measured by gel permeationchromatography (GPC) using polystyrene standards (Mw, hereinafter merelyreferred to as a weight-average molecular weight) of the novolak resinis preferably from 1000 to 10000, and particularly preferably from 2000to 8000, in view of heat resistance, rectangularity of pattern,dependence of resist profile on pattern, resolving power, and increasein sensitivity.

Reaction With Crosslinking Agent

Pretreatment of Novolak Resin

In the case of reacting a novolak resin with a crosslinking agent, thepresence of an acid component in the reaction system is not preferablein view of storage stability as a resist solution in a bottle afterresist preparation. Therefore, it is preferred to reliably conduct theoperation of removing the acid component contained in the novolak resinbefore reacting with the crosslinking agent. The acid component is anacid catalyst used to synthesize the novolak resin, or an acid componentsuch as free acid which exists in a reaction solvent used duringsynthesis, and can be analyzed by gas chromatography.

Examples of methods of removing the acid component includeconventionally known methods, for example, use of an ion exchange resin,washing with pure water, and neutralization with alkali.

In particular, the method using the ion exchange resin is preferablebecause the organic acid can be reliably reduced. The method can beconducted by dissolving 100 g of a novolak resin in a mixed solvent of300 to 600 g of methanol and 30 to 60 g of pure water and purifying thenovolak resin solution using an ion exchange resin.

Examples of the ion exchange resin include highly purified monobed resinfor use in ultrapure water and, for example, AMBERLITE EG-4 andAMBERLITE EG-290 manufactured by Rohm and Haas Company can be preferablyused.

Examples of the purification method include (1) column method and (2)batch method. The column method (1) can be conducted by passing thenovolak resin solution through a column filled with an ion exchangeresin hydrated sufficiently with pure water one to several times. Thebatch method (2) can be conducted by weighing an ion exchange resinhydrated sufficiently with pure water (in an amount of about 10% byweight based on the solid content of the novolak resin), charging theion exchange resin in a beaker containing the novolak resin solution,stirring for about one hour and filtering with a filter paper. Hydrationis preferably conducted under the conditions in accordance with themethod of use of the exchange resin.

The concentration of the acid component in the novolak resin ispreferably adjusted to 0.1 ppm or less, and particularly preferably 0.01ppm or less, before the reaction with the crosslinking agent.

Crosslinking Agent

In the crosslinking agent represented by the general formula (VI), R¹ isa branched, linear, or cyclic alkylene group having 1 to 10 carbon atomswhich may have a substituent, or a substituent represented by thegeneral formula (II). The alkylene group may have an oxygen bond (etherbond) in the main chain.

In the general formula (II), R⁴ is a branched, linear or cyclic alkylenegroup having 1 to 10 carbon atoms which may have a substituent, and thealkylene group may have an oxygen bond (ether bond) in the main chain.R¹ is preferably —C₄H₈—, —C₂H₄OC₂H₄—, —C₂H₄OC₂H₄OC₂H₄—, or a substituentrepresented by the general formula (II), more preferably a substituentrepresented by the general formula (II). It is particularly preferablethat R⁴ have one carbon atom and that m be 1.

The content of the crosslinking agent is from 3 to 15% by weight, andpreferably from 4 to 8% by weight, based on the solid content of thenovolak resin. When the content is less than 3% by weight, reduction infilm thickness of the unexposed area of the resist pattern becomessevere and contrast of the resist pattern tends to deteriorate. On theother hand, when the content exceeds 15% by weight, solubility in adeveloper solution (aqueous alkali solution) tends to drasticallydecrease, thus causing a problem that sensitivity is poor and resolutionof a pattern is not achieved. Since the reaction between the novolakresin and the crosslinking agent proceeds without using an acidcatalyst, the use of the acid catalyst is not essential and it ispreferable to use no acid catalyst in view of storage stability as aresist solution in a bottle of the resist composition.

After reacting with the crosslinking agent, the weight-average molecularweight of the component (A) is preferably from 10000 to 70000, andparticularly preferably from 20000 to 50000, in view of heat resistance,rectangularity of pattern, dependence of resist shape on pattern,resolving power, and increase in sensitivity.

As described above, by removing the acid component from the novolakresin before the reaction or using no acid catalyst upon reaction, itbecomes possible to preferably adjust the concentration of an acid inthe component (A) after reacting with the crosslinking agent to 10 ppmor less, more preferably 1 ppm or less, and most preferably 0.1 ppm orless.

In the reaction between the novolak resin and the crosslinking agent,for example, after removing the acid component from the novolak resin,the novolak resin is dissolved in the reaction solvent and the solutionis concentrated, thereby removing methanol and water remaining in thenovolak resin and adjusting the solid content. The solid content ispreferably adjusted to about 30% by weight. After the inner temperatureis preferably controlled within a range from about 100 to 110° C. byheating, stirring is conducted under the same temperature conditions anda crosslinking agent solution whose solid content is adjusted to about10 to 50% by weight using the reaction solvent is added dropwise inseveral portions.

After the completion of dropwise addition, stirring is continuouslyconducted while maintaining the temperature for about 24 hours, theinterior temperature is reduced to room temperature (about 25° C.) andstirring is further conducted under the same temperature conditions forabout 12 hours to obtain a component (A). Then, the solvent is replacedby an organic solvent used in the preparation of a resist composition toobtain a mixture of the component (A) and the organic solvent.

Since the acid does not exert a severe influence on the reaction betweenthe novolak resin and the crosslinking agent, it is not necessary tosecurely control the concentration of the acid in the reaction.

As the reaction solvent, solvents such as methyl isobutyl ketone andγ-butyrolactone can be appropriately used.

As the crosslinking agent, there can also be used the same crosslinkingagent as in the second aspect described hereinafter.

Component (A′)

The component (A′) is a slightly alkali-soluble or alkali-insolublepolyhydroxystyrenic resin having a property that solubility in anaqueous alkali solution is enhanced in the presence of an acid,comprising either or both of a constituent unit (a′1) and theintermolecular crosslinked moiety (a′2).

The component (A′) can be synthesized by using a hydroxystyrenic resinin place of the novolak resin in the component (A) and reacting thehydroxystyrenic resin with the crosslinking agent.

The mechanism in which solubility in the aqueous alkali solution variesis the same as in the case of the component (A).

The hydroxystyrenic resin is not specifically limited as long as it iscommonly used in the resist composition and comprises a hydroxystyreneconstituent unit. Examples thereof include homopolymer ofhydroxystyrene, copolymer of hydroxystyrene and the otherhydroxystyrenic monomer or styrenic monomer, and copolymer ofhydroxystyrene and acrylic acid or methacrylic acid or its derivative.

The content of the hydroxystyrene constituent unit in thehydroxystyrenic resin is at least 50 mol % or more, and preferably 70mol % or more, in view of reactivity of the crosslinking agent.

In particular, a copolymer comprising a hydroxystyrene constituent unitand at least a styrene constituent unit is preferable because theresulting resist composition has high heat resistance and highsensitivity and the effect of improving shape of a linear resist patternis exerted. As described above, when the resin component comprisingessentially a styrene constituent unit is reacted with the crosslinkingagent, the component (A″) is obtained. Among these, a copolymercomprising a hydroxystyrene constituent unit and a styrene constituentunit is preferable.

The styrene constituent unit refers to a constituent unit represented bythe formula (II′) of the second aspect described hereinafter.

The content of the styrene constituent unit is preferably from 1 to 30mol %, and more preferably from 5 to 15 mol %, in view of reliability ofreactivity with the crosslinking agent and improvements in heatresistance and sensitivity.

The weight-average molecular weight of the hydroxystyrenic resin ispreferably from 1000 to 8000, and particularly preferably from 2000 to5000, in view of heat resistance, rectangularity of pattern, dependenceof resist shape on pattern, resolving power, increase in sensitivity,and stability of the reaction with the crosslinking agent.

Reaction With Crosslinking Agent

Pretreatment of Hydroxystyrenic Resin

The hydroxystyrenic resin and the crosslinking agent are commonlyreacted in the presence of an acid catalyst. As the acid catalyst, therecan be used those exemplified in the description of the synthesis of thenovolak resin.

In the case of reacting the hydroxystyrenic resin with the crosslinkingagent, the content of the entire acid component containing the acidcatalyst is preferably adjusted within a range from 10 to 1000 ppm, andpreferably from 50 to 500 ppm, based on the solid content of the resin.Since the hydroxystyrenic resin itself contains very low levels of acidimpurities, the concentration of the acid in the reaction system duringreaction is almost the same as that of the acid catalyst to be added asthe catalyst, and thus the concentration of the acid upon reaction canbe controlled by the amount of the acid catalyst.

When the content exceeds 1000 ppm, it is not preferable in view ofstorage stability as a resist solution in a bottle after resistpreparation. On the other hand, when the content is less than 10 ppm,the reaction may not proceed because insufficient catalytic effect isexerted upon crosslinking.

After the reaction, the operation of removing the acid componentcontained in the reaction product is preferably conducted, if necessary.The acid component can be removed by the same method as in the case ofthe novolak resin.

As a result, the concentration of the acid in the styrenic resin afterthe reaction can be adjusted to preferably 10 ppm or less, and morepreferably 1 ppm or less, in the component (A′).

After the crosslinking reaction sufficiently proceeded, a basic compoundsuch as pyridine can be used for the purpose of controlling orterminating the crosslinking reaction.

In view of stability over time of the resin after the reaction, basiccompound is preferably used in the amount of about 1 to 5% by weightbased on the solid content of the resin.

After reacting with the crosslinking agent in such a manner, theweight-average molecular weight of the component (A′) is preferably from50000 to 150000, and particularly preferably from 60000 to 100000, inview of heat resistance, rectangularity of pattern, dependence of resistshape on pattern, resolving power, increase in sensitivity, suppressionof reduction in film thickness of the unexposed area, and an improvementin coatability.

Crosslinking Agent

As the crosslinking agent, there can be used those exemplified in thedescription of the component (A).

The content of the crosslinking agent is from 3 to 15% by weight, andpreferably from 5 to 10% by weight, based on the solid content of thehydroxystyrenic resin. When the content is less than 3% by weight,reduction in film thickness of the unexposed area of the resist patternbecomes severe and contrast of the resist pattern tends to deteriorate.On the other hand, when the content exceeds 15% by weight, solubility ina developer solution (aqueous alkali solution) tends to drasticallydecrease, thus causing a problem that sensitivity is poor and resolutionof a pattern is not achieved.

In the reaction between the hydroxystyrenic resin and the crosslinkingagent, for example, after synthesizing the hydroxystyrenic resin andoptionally removing the acid component, the hydroxystyrenic resin isdissolved in the reaction solvent and the solution is concentrated,thereby removing methanol and water remaining in the hydroxystyrenicresin and adjusting the solid content. The solid content is preferablyadjusted to about 30% by weight.

After an acid catalyst is added to the concentrated solution and theinner temperature is preferably controlled within a range from about 100to 110° C. by heating, stirring is conducted under the same temperatureconditions and a crosslinking agent solution whose solid content isadjusted to about 10 to 50% by weight using the reaction solvent isadded dropwise in several portions. After the completion of dropwiseaddition, stirring is continuously conducted while maintaining thetemperature for about 20 hours, inner temperature is reduced to roomtemperature (about 25° C.) and stirring is further conducted under thesame temperature conditions for about one hour. Then, an organic solventsuch as 2-heptanone used in the preparation of a resist composition isadded and dissolved.

The solution is washed several times with a solution, for example,methanol/water to remove the acid component. After separating theorganic layer such as 2-heptanone, the residue was concentrated and theremaining methanol/water was removed to obtain a mixture of thecomponent (A′) and the organic solvent.

Examples of the reaction solvent include methyl isobutyl ketone andγ-butyrolactone. Since the acid exerts severe influence on the reactionbetween the hydroxystyrenic resin and the crosslinking agent, it isnecessary to securely control the concentration of the acid in thereaction and stable γ-butyrolactone having less acid content ispreferably selected.

The resist composition of this aspect may contain either or both of thecomponents (A) and (A′) (preferably the component (A″)). As thecomponents (A) and (A′) (preferably the component (A″)), one or moredifferent kinds may be used in combination.

Component (B)

The component (B) is not specifically limited and examples thereofinclude photo acid generators which are conventionally known asconstituent material of a chemical amplification type positivephotoresist composition.

For example, there can be used sulfonylazomethane photo acid generators,onium salt photo acid generators and oxime sulfonate photo acidgenerators.

Among these photo acid generators, those having i-ray absorption arepreferable because a conventional i-ray stepper can be employed as itis. In this case, a resist composition suited for i-rays can beobtained.

Examples of the component (B) suited for i-ray exposure including thefollowing compounds.

Compounds represented by the following general formulas (ii) and (iii):

wherein m′ represents 0 or 1; X represents 1 or 2; R₁ represents aphenyl group which may be substituted with one or more alkyl groupshaving 1 to 12 carbon atoms, a heteroaryl group, or an alkoxycarbonylgroup having 2 to 6 carbon atoms, a phenoxycarbonyl group or CN when m′is 0; R₁′ represents an alkylene group having 2 to 12 carbon atoms; R₂represents a phenyl group which may be substituted with one or morealkyl groups having 1 to 12 carbon atoms, a heteroaryl group, or analkoxycarbonyl group having 2 to 6 carbon atoms, phenoxycarbonyl groupor CN when m′ is 0; R₃ represents an alkyl group having 1 to 18 carbonatoms; R₃′ represents an alkyl group having 1 to 18 carbon atoms whenX=1, or an alkylene group having 2 to 12 carbon atoms or a phenylenegroup when X=2; R₄ and R₅ each independently represents a hydrogen atom,halogen, or an alkyl group having 1 to 6 carbon atoms; A represents S, Oor NR₆; and R₆ represents a hydrogen atom or a phenyl group (U.S. Pat.No. 6,004,724). Specific examples thereof include thiolene-containingoxime sulfonate represented by the following formula (VII):

There is also exemplified a bis(trichloromethyl)triazine compoundrepresented by the following formula (iv):

wherein R⁶ and R⁷ each represents alkyl group having 1 to 3 carbonatoms, or a combination of the compound (iv) and abis(trichloromethyl)triazine compound represented by the followingformula (v):

wherein Z represents a 4-alkoxyphenyl group (Japanese PatentApplication, First Publication No. Hei 6-289614 and Japanese PatentApplication, First Publication No. Hei 7-134412).

Specific examples of the triazine compound (iv) include2-[2-(3,4-dimethoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(3-methoxy-4-ethoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(3-methoxy-4-propoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(3-ethoxy-4-methoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(3,4-diethoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(3-ethoxy-4-propoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(3-propoxy-4-methoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(3-propoxy-4-ethoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazineand2-[2-(3,4-dipropoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine.These triazine compounds may be used alone or in combination.

Examples of the triazine compound (v), which is optionally used incombination with the triazine compound (iv), include2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine,2-(4-ethoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine,2-(4-propoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine,2-(4-butoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine,2-(4-methoxynaphthyl)-4,6-bis(trichloromethyl)-1,3,5-triazine,2-(4-ethoxynaphthyl)-4,6-bis(trichloromethyl)-1,3,5-triazine,2-(4-propoxynaphthyl)-4,6-bis(trichloromethyl)-1,3,5-triazine,2-(4-butoxynaphthyl)-4,6-bis(trichloromethyl)-1,3,5-triazine,2-(4-methoxy-6-carboxynaphthyl)-4,6-bis(trichloromethyl)-1,3,5-triazine,2-(4-methoxy-6-hydroxynaphthyl)-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(2-furyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(5-methyl-2-furyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(5-ethyl-2-furyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(5-propyl-2-furyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,(3,5-dimethoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(3-methoxy-5-ethoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(3-methoxy-5-propoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(3-ethoxy-5-methoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(3,5-diethoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(3-ethoxy-5-propoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(3-propoxy-5-methoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-[2-(3-propoxy-5-ethoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-2-(3,5-dipropoxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine,2-(3,4-methylenedioxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine and2-[2-(3,4-methylenedioxyphenyl)ethenyl]-4,6-bis(trichloromethyl)-1,3,5-triazine.These triazine compounds may be used alone or in combination.

There is also exemplified a compound represented by the followingformula (vi):

wherein Ar represents a substituted or unsubstituted phenyl group or anaphthyl group; R″ represents an alkyl group having 1 to 9 carbon atoms;and n′ represents an integer of 2 or 3. These compounds may be usedalone or in combination. Among these compounds, a compound representedby the formula (VII) and a compound represented by the following formula(vii) are preferably used because they are excellent in acid generationefficiency to i-rays.

As the component (B), one or more kinds can be used.

The amount of the component (B) is preferably from 0.5 to 5 parts byweight, and preferably from 1 to 4 parts by weight, based on 100 partsby weight of the solid content of the resin. When the amount is lessthan 0.5 parts by weight, sufficient pattern formation may not occur. Onthe other hand, when the amount exceeds 5 parts by weight, reduction infilm thickness of the unexposed area tends to becomes severe and storagestability as a resist solution by particles of the resist compositiontends to deteriorate, unfavorably.

Component (C)

The resist composition of this aspect preferably contains a basiccompound (preferably an amine) as the component (C) so as to enhancestorage stability.

The compound is not specifically limited as long as it has compatibilitywith the resist composition, and examples thereof include a compounddescribed in Japanese Patent Application, First Publication No. Hei9-6001. The disclosure of Japanese Patent Application, First PublicationNo. Hei 9-6001 is incorporated by reference herein.

Among these, a tertiary amine is preferable, and tri-n-octylamine andtri-n-decylamine are particularly preferable in view of storagestability as a resist solution in a bottle. Also pyridine compounds,particularly 2,6-lutidine is preferable because of excellent PED (postexposure delay) after exposure.

As the component (C), one or more kinds can be used in combination.

The content of the component (C) is preferably from 0.01 to 5.0 parts byweight, and particularly preferably from 0.1 to 1.0 parts by weight,based on 100 parts by weight of the solid content of the resin in viewof the effect.

Organic Solvent

The organic solvent is not specifically limited as long as it is used inthe chemical amplification type positive resist composition.

Examples thereof include ester solvents such as propylene glycolmonoalkyl ether acetate (for example, propylene glycol monomethyl etheracetate (PGMEA)) and lactate ester (for example, ethyl lactate); andnon-ester solvents, for example, ketones such as acetone, methyl ethylketone, cyclohexanone, methyl isoamyl ketone and 2-heptanone, polyhydricalcohols such as ethylene glycol, propylene glycol, diethylene glycol,or their derivatives such as monomethyl ether, monoethyl ether,monopropyl ether, monobutyl ether or monophenyl ether of polyhydricalcohols, and cyclic ethers such as dioxane. The ester solvents arereaction products of the organic carboxylic acid and the alcohol andtherefore contain an organic carboxylic acid such as a free acid.Therefore, in the resist composition containing no component (C) or theresist composition containing no storage stabilizer describedhereinafter, non-ester solvents containing no free acid are preferablyselected and ketones (ketone solvents) are preferable. Among these,2-heptanone is particularly preferable in view of coatability andsolubility of the component (B).

Both ester and non-ester solvents are sometimes decomposed over time toproduce an acid as by-product; however, the decomposition reaction issuppressed in the presence of the component (C) or the storagestabilizer described hereinafter. The ester solvents exert a remarkableeffect and are preferable in the presence of the component (C) and thestorage stabilizer, and PGMEA is particularly preferable.

It has been confirmed that the acid component as a by-product producedfrom the decomposition is formic acid, acetic acid or propionic acid inthe case of 2-heptanone.

One or more organic solvents can be used alone or in combination.

The organic solvent is used so that the solid content of the resistcomposition falls within a range from 20 to 50% by weight, andpreferably from 25 to 45% by weight, in view of coatability.

The resist composition of this aspect preferably contains the followingstorage stabilizers, if necessary.

In addition to the ester solvents, non-ester solvents are sometimesdecomposed to produce an acid component as a by-product.

In such a case, the storage stabilizer is preferably added.

The storage stabilizer is not specifically limited as long as it has anaction of suppressing the decomposition reaction of the solvent, andexamples thereof include antioxidants described in Japanese PatentApplication, First Publication No. Sho 58-194834. The disclosure ofJapanese Patent Application, First Publication No. Sho 58-194834 isincorporated by reference herein. As the antioxidant, a phenoliccompound and an amine compound are known and the phenolic compound ispreferable. Particularly, 2,6-di(tert-butyl)-p-cresol and its derivativeare preferable because they are effective against deterioration of theester solvent and the ketone solvent and are commercially available, andare also inexpensive and excellent in storage stabilization effect. Inparticular, they are excellent in deterioration preventing effect topropylene glycol monoalkyl ether acetate and 2-heptanone.

The content of the storage stabilizer is preferably from 0.01 to 3 partsby weight, and particularly preferably from 0.1 to 1.0 parts by weight,based on 100 parts by weight of the solid content of the resin.

When the content is less than the above range, sufficient storagestabilization effects cannot be obtained. On the other hand, when thecontent exceeds the above range, it is not preferable in view ofreduction in film thickness of the top portion of the resist patternshape, deterioration in sensitivity, and change in exposure margin.

Since the resist composition used in a thick-film photolithographyprocess (hereinafter sometimes abbreviated to “for thick-film” or “forthick-film process”) described hereinafter commonly has high resistconcentration (solid content), it can cause deposition of foreign matterbecause of unstable solubility in the resist of the component (B). Insuch a case, solvent stabilizers are preferably added in thecomposition.

The solid content of the resist composition for thick-film is adjustedwithin a range from 25 to 50% by weight, and preferably from 30 to 40%by weight, in view of coatability of the thick film.

As the solvent stabilizer, γ-butyrolactone is particularly preferable.

The content of the solvent stabilizer is preferably within a range from1 to 10 parts by weight, and particularly preferably from 3 to 7 partsby weight, based on 100 parts by weight of the solid content of theresist composition.

When the content is less than the above range, deposition of thecomponent (B) or deterioration over time of foreign matter occurs. Onthe other hand, when the content exceeds the above range, it is notpreferred in view of deterioration of residual film property ofunexposed area.

To the resist composition of this aspect, there can be optionally addedadditives having compatibility, for example, additive resins,plasticizers, stabilizers and surfactants used for improvingperformances of the resist film; colorants used for further visualizingthe developed images; sensitizers and antihalation dyes used for furtherimproving the sensitization effect; and conventional additives such asadhesion improvers; as long as the object of the present invention isnot adversely affected.

The concentration of the acid component in the resist composition ispreferably 10 ppm or less, more preferably 8 ppm or less, and mostpreferably 5 ppm or less, in view of storage stability as a resistsolution in a bottle. The closer to zero, the more preferable, and thusthere is no technical meaning in limitation of the lower limit.

As described above, the concentration of the acid component can beadjusted by performing a treatment of decreasing the concentration ofthe acid component in the components (A) and (A′) to be as low aspossible, using an organic solvent which is less likely to generate anacid component, adding tertiary amine, or adding a storage stabilizer.

In the component (A′), the component (A″) comprising a hydroxystyreneconstituent unit and a styrene constituent unit is preferably usedbecause the resist composition has high heat resistance and highsensitivity and the effect of improving shape of a linear resist patternis exerted.

In view of these effects, it is not necessarily essential to adjust thecontent of the acid component to 10 ppm or less in the positivephotoresist composition.

When the chemical amplification type positive photoresist composition(third example) using the component (A″) comprises a crosslinkedstructure obtained by reacting with the crosslinking agent and a styreneconstituent unit, the resulting resist composition has high heatresistance and high sensitivity and the effect of improving shape of alinear resist pattern is exerted.

Method For Formation of Resist Pattern

The resist composition thus formed is suited for use in a so-calledthick-film process wherein a film thickness is from about 2 to 7 μm.

The thick-film resist pattern can be employed as a resist for highenergy implantation or a resist for metal wiring.

In particular, heat resistance is required of the resist composition forthick-film. The resist composition of this aspect is excellent in heatresistance and is highly sensitized, and therefore it can sufficientlymeet the level required.

Preferable methods for use of the resist composition of this aspect willnow be described by way of mainly a thick-film photolithography process(hereinafter referred to as a thick-film process).

First, a resist composition prepared by dissolving various components inan organic solvent is applied on a substrate such as a silicon waferusing a spinner, and this is then prebaked to form a thick resist film(photosensitive layer) having a thickness of about 2 to 7 μm. Then, theresist film is selectively exposed via a desired mask pattern byirradiating with light, preferably i-rays (365 nm) using a light sourcesuch as a low-pressure mercury lamp, high-pressure mercury lamp orultrahigh-pressure mercury lamp. Then, when the resist film wassubjected to a PEB (post exposure bake) treatment is conducted underheating conditions at about 90 to 150° C. and it is dipped in adeveloper solution, for example, an aqueous alkali solution such asaqueous 1-10 wt % solution of tetramethylammonium hydroxide (TMAH), andthe exposed area is dissolved and removed to obtain images which arefaithful to the mask pattern. Then, postbaking is conducted underheating conditions of about 90 to 140° C. to form a resist pattern forthick-film process.

The resist pattern has excellent rectangular shape even under thick-filmconditions of about 2 to 7 μm. Therefore, it is suited for use as aresist film for implantation or metal wiring.

The resist composition of this aspect exerts the following effects.

That is, it is excellent in storage stability as a resist solution in abottle.

Also, it has advantages such as low cost.

Since a large amount of very expensive materials are used, both aconventional resist composition containing an alkali soluble resin andPAC as a main component and chemical amplification type photoresistcomposition containing an acid dissociable group-containing resin and aphoto acid generator as a main component have a problem in that it isimpossible to cope with recent reductions in production cost because ofhigh material cost. In the former, expensive materials are PAC andsensitivity improvers (sensitizers). In the latter, expensive materialsare mono-dispersed polyhydroxystyrene synthesized by living anionpolymerization and a resin component having a special acid dissociablegroup.

In the resist composition of this aspect, cost reduction can be madebecause these materials need not necessarily be used.

According to the resist composition of this aspect, it is made possibleto obtain a resist pattern which is excellent in rectangularity ofprofile and also has good shape.

The resist composition of this aspect is excellent in heat resistance,sensitivity behavior, and rectangularity of the profile and is thereforesuited for formation of a thick-film resist pattern for implantation ormetal wiring.

Upon metal wiring formation, a heat treatment at high temperature,referred to as postbake after formation of a resist pattern so as toimprove heat resistance upon implantation, is commonly conducted. Theresist pattern formed by using a conventional resist composition has aproblem that taper shape is further enlarged upon postbaking.

Since the rectangular shape of the resist pattern is reliably requiredin the implantation, it is necessary to realize a material capable offorming a resist pattern having an excellent rectangular shape.

In this aspect, there is exerted the effect of maintaining therectangular shape of the resist pattern even after postbaking.

The resist composition of this aspect exhibits low dependence on patternsize and, for example, a resist pattern having an excellent rectangularshape can be obtained even when a fine resist pattern having a width ofabout 1 μm is formed. Also, when a very large resist pattern having alarge width of more than 100 μm is formed, the profile is not taperedand has good shape.

As described above, since both fine pattern and rough pattern can beobtained as patterns having good shape, the photoresist composition ofthis aspect is suited for use in which patterns having different sizesare formed on a substrate at a time, for example, in a system LCD.

Second Aspect

Chemical Amplification Type Positive Photoresist Composition

The chemical amplification type positive resist composition of thesecond aspect is a two-component chemical amplification type positivephotoresist composition comprising (A2) a resin made of a reactionproduct of (A1) an alkali soluble resin and (C1) a crosslinkingpolyvinyl ether compound wherein alkali solubility enhances by an actionof an acid, and (B1) a photo acid generator generating acid underirradiation with radiation, wherein

the component (A1) comprises a unit (a1′) derived from(α-methyl)hydroxystyrene represented by the above general formula (I′)and an alkali-insoluble unit (a2′) having no acid dissociabledissolution inhibiting group, and wherein a dissolution rate to anaqueous 2.38% by weight solution of the component (A1) in TMAH(tetramethylammonium hydroxide) is from 10 to 100 nm/second.

(A2) Resin made of reaction product of the components (A1) and (C1)wherein alkali solubility is enhanced by an action of an acid.

First, the reaction product of the components (A1) and (C1) (hereinafterreferred to as a component (A2)) will now be described.

Component (A2)

The component (A2) is a reaction product obtained by reacting thecomponent (A1) with the component (C1) and is slightly soluble orinsoluble in an aqueous alkali solution, and also has a property thatalkali solubility is enhanced by an action of an acid.

When the component (A1) is reacted with the component (C1), there isobtained a reaction product comprising a constituent unit wherein oneterminal vinyl group of the component (C1) is linked to phenolichydroxyl groups in the side chain of the component (A1).

Specific examples of the constituent unit include a constituent unitrepresented by the following general formula (2A).

When the component (A1) is reacted with the component (C1), there isobtained a reaction product comprising a moiety wherein both terminalvinyl groups of the component (C1) are linked to two phenolic hydroxylgroups in the side chain of the component (A1). Specific examples of theconstituent unit include inter-molecular crosslinking unit representedby the following general formula (2B).

There is commonly obtained a reaction product (a) comprising bothconstituent unit (for example, (2A)) wherein only one terminal group ofthe component (C1) is linked and a moiety (for example, (2B)) whereinboth terminal groups are linked.

R¹² is the same as in the general formula (III′) described hereinafter.

The component (A2) in this example can be preferably obtained byreacting the component (A1) with the component (C1) in the substantialabsence of an acid catalyst. Consequently, a crosslinked structure dueto component (C1) is formed in the component (A1) and the base resin(A2) in the resist composition preferably becomes slightly soluble orinsoluble in an aqueous alkali solution such as alkali developer used toform a resist pattern.

By preliminarily linking the component (C1) with hydroxyl groups in theside chain of the alkali soluble resin (A1), change over time of thechemical amplification type positive photoresist composition issuppressed and thus a material with less change in sensitivity isobtained.

When the chemical amplification type positive photoresist composition isapplied and heated, a resist coating film is formed. At this time, whenthe unreacted phenolic hydroxyl groups in the side chain of thecomponent (A2) remain, they react with terminal vinyl groups of theconstituent unit (A2) to form a crosslinked structure.

When an acid generated from the component (B1) under exposure reactswith the component (A2) having the crosslinked structure, thecrosslinked structure is cleaved and solubility of the component (A2) inan aqueous alkali solution is enhanced.

In this embodiment, since the component (A1) is preliminarily reactedwith the component (C1), it is not necessary to enable the crosslinkingreaction to proceed upon prebaking and the prebaking temperatureconditions are less likely to be limited. Specifically, the crosslinkingreaction can proceed at a temperature of 120° C. or lower.

In the case of reacting the component (A1) with the component (C1), itis preferred to securely control the concentration of the acidcomponent. In view of stability over time, it is not preferred that thecomponent (A1) contain the acid component as impurities. Therefore, itis preferred to securely conduct the operation of removing the acidcomponent contained in the component (A1) before reacting with thecomponent (C1). The acid component can be analyzed by gaschromatography. Examples of the method of removing the acid componentinclude conventionally known methods, for example, use of an ionexchange resin, washing with pure water, and neutralization with alkali.

The concentration of the acid component in the component (A1) beforereacting with the component (C1) is preferably adjusted to 0.1 ppm orless, and particularly preferably 0.01 ppm or less.

The content of the component (C1) is from 5 to 50% by weight, andpreferably 10 to 30% by weight, based on the component (A1). When thecontent is more than the lower limit, it is made possible to preventsuch a disadvantage that the crosslinking reaction does not sufficientlyproceed and contrast between the unexposed area and the exposed areadeteriorates. When the content is less than the upper limit, it is madepossible to prevent such a disadvantage that uniformity of thecomposition in the resist coating film cannot be obtained andlithographic properties deteriorate.

The weight-average molecular weight (Mw: value as measured by gelpermeation chromatography using polystyrene standards) of the component(A2) is, for example, from 20000 to 150000, and preferably 30000 to100000, in view of stability with time and reduction in defects. Whenthe weight-average molecular weight is within the above range, it ismade possible to prevent such a disadvantage that the resultingcomposition becomes insoluble in a solvent and dry etching resistancedeteriorates.

The dispersion degree (Mw/Mn: Mn is a number-average molecular weight)of the component (A2) is preferably from 1.0 to 5.0, and more preferably1.0 to 3.0, in view of improvement in resolution and reduction indefects. The component (A2) is preferably used in a two-componentamplification type positive photoresist composition containing acomponent (B1) described hereinafter.

(A1) Alkali Soluble Resin

Unit (a1′) Derived From (α-methyl)hydroxystyrene

When the component (A1) comprises a constituent unit (a1′), the entirecomponent (A1) becomes soluble in alkali and a crosslinking reactionproduct of the components (A1) and (C1) can be obtained by the reactionwith the component (C1) or heating upon prebaking.

In the formula (I′), R is a hydrogen atom or a methyl group and ispreferably a hydrogen atom.

In view of availability, 1 is preferably 1.

The hydroxyl group may be substituted on any of the o-, m- and thep-positions. When 1 is 2 or 3, any substitution positions can becombined. When 1 is 1, the hydroxyl group may be substituted on any ofthe o-, m- and p-positions, and preferably p-position in the view ofeasily availability and low price.

The term “(α-methyl)hydroxystyrene” means either or both ofhydroxystyrene and α-methylhydroxystyrene. The term “constituent unitderived from (α-methyl)hydroxystyrene” means a constituent unitconstituted by cleavage of ethylenical double bonds of(α-methyl)hydroxystyrene.

In claims and the specification, the term “unit” or “constituent unit”means a monomer unit constituting a polymer.

The content of the constituent unit (a1′) in the component (A1) ispreferably 60 mol % or more, more preferably from 70 to 90 mol %, andmost preferably from 75 to 85 mol %, in view of control of solubilitydue to the reaction with the component (C1).

Alkali-insoluble unit (a2′) having no acid dissociable dissolutioninhibiting group

In the constituent unit (a2′), the term “having no acid dissociabledissolution inhibiting group” means that a constituent unit whereinhydrogen atom of the hydroxyl group is substituted with an aciddissociable alkali dissolution inhibiting group such as t-boc(tert-butoxycarbonyl) group or ethoxyethyl group in a unit having aphenolic hydroxyl group, and a tertiary ester constituent unit as a(meth)acrylate unit ((meth)acrylate means either or both of acrylate andmethacrylate) wherein an OH group of a carboxyl group of a constituentunit derived from (meth)acrylic acid is substituted with a tertiaryalkyloxy group are excluded.

When the resist composition of this aspect comprises a constituent unit(a2′) which is scarcely influenced by the acid component generated fromthe component (B1) described hereinafter and is also alkali-insoluble(insoluble in an alkali developer solution), it is made possible toprevent swelling of a resist pattern due to alkali development and toimprove resolution of a fine pattern.

The constituent unit (a2′) is not specifically limited as long as it hasno acid dissociable dissolution inhibiting group and isalkali-insoluble, as described above, but is preferably a unit derivedfrom (α-methyl)styrene represented by the following general formula(II′):

wherein R represents a hydrogen atom or a methyl group, R¹¹ representsan alkyl group having 1 to 5 carbon atoms and p represents an integer of0 or 1 to 3, because of excellent dry etching resistance.

The term “(α-methyl)styrene” means either or both of styrene andα-methylstyrene. The term “constituent unit derived from(α-methyl)styrene” is apparent from the general formula (II′) and meansa constituent unit constituted by cleavage of ethylenical double bondsof (α-methyl)styrene.

In the formula (II′), R¹¹ is a linear or branched alkyl group having 1to 5 carbon atoms and examples thereof include methyl group, ethylgroup, propyl group, isopropyl group, n-butyl group, isobutyl group,tert-butyl group, pentyl group, isopentyl group and neopentyl group.Among these groups, a methyl group or an ethyl group is preferably froman industrial point of view.

p is an integer 0 or 1 to 3. Among these, p is preferably 0 or 1, andparticularly preferably 0 from an industrial point of view.

When p is from 1 to 3, R³ may be substituted on any of the o-, m- andp-positions. When p is 2 or 3, any substitution positions can becombined.

The content of the constituent unit (a2′) in the component (A1) ispreferably from 5 to 35 mol %, more preferably 10 to 30 mol %, and mostpreferably from 15 to 25 mol %. When the content is more than the lowerlimit, it is made possible to suppress a disadvantage such as reductionin film thickness of the unexposed area upon development and to improveresolution. It is also made possible to prevent swelling of a resistpattern due to alkali development and to improve resolution of a finepattern. Control of the content to the upper limit or less easily makesthe resulting composition soluble in an organic solvent.

Dissolution Rate

In this aspect, a dissolution rate of the component (A1) to an aqueous2.38% wt % solution of TMAH (tetramethylammonium hydroxide) is from 10to 100 nm/second, and preferably from 20 to 80 nm/second.

In the case of a small dissolution rate such as 100 nm/second or less,resolution is improved. The reason is believed to be as follows. Thatis, as described hereinafter, the crosslinked structure formed betweenthe components (C1) and (A1) is dissolved in an alkali developersolution as a result of cleavage by an action of an acid at the exposedarea, while the unexposed area is not dissolved in the alkali developersolution, and thus contrast at the interface can be enhanced. Also, theeffect of reducing defects can be exerted.

By adjusting to 10 nm/second or more, a resist can be prepared bydissolving in an organic solvent.

The dissolution rate can be adjusted by varying the content of theconstituent units (a1′) and (a2′). For example, the dissolution rate canbe decreased by increasing the content of the constituent unit (a2′).

Specifically, the value of the dissolution rate is a value obtained inthe following manner.

First, a solution prepared by dissolving the component (A1) in anorganic solvent is applied on a silicon wafer and the organic solvent isvaporized by a heat treatment to form a resin coating film (thickness:500 to 1300 nm, for example, 1000 nm). The organic solvent isappropriately selected from conventionally known organic solvents, whichare described hereinafter, used in the chemical amplification typepositive photoresist composition. The concentration of the component(A1) can be adjusted to the same concentration as in the resistcomposition, for example, 10 to 25% by weight, particularly 20% byweight. After measuring the thickness of the resin coating film, thewafer is immersed in an aqueous 2.38 wt % TMAH solution at 23° C. Then,the time required to completely dissolve the resin film is measured andreduction in film thickness per unit time (nm/second) of the resincoating film is determined therefrom.

The resulting reduction in film thickness of the resin coating film is adissolution rate of the component (A1).

The component (A1) may comprise a constituent unit, which iscopolymerizable with the constituent units (a1′) and (a2′), in additionto the constituent units (a1′) and (a2′). The total content of theconstituent units (a1′) and (a2′) is preferably 80 mol % or more, andpreferably 90 mol %, and most preferably 100 mol %. In view of reductionin defects, the component (A1) preferably comprises the constituentunits (a1′) and (a2′).

The component (A1) can be mixed with one or more kinds of resins havingdifferent weight-average molecular weights and resins having differentconstituent units.

The component (A1) can be prepared by conventionally known radicalpolymerization or living anion polymerization of a monomer from whichthe units (a1′) and (a2′) are derived.

The weight-average molecular weight (Mw: value as measured by gelpermeation chromatography using polystyrene standards) of the component(A1) is preferably from 1500 to 30000, more preferably 2000 to 20000,and most preferably from 3000 to 20000, in view of stability over timeand reduction in defects. When the weight-average molecular weight iswithin the above range, it is made possible to prevent such adisadvantage that the resulting composition becomes insoluble in asolvent and dry etching resistance deteriorates.

The dispersion degree (Mw/Mn: Mn is a number-average molecular weight)of the component (A1) is preferably from 1.0 to 5.0, and more preferably1.0 to 3.0, in view of improvement in resolution and reduction indefects.

(C1) Crosslinking Polyvinyl Ether Compound

The component (C1) serves as a crosslinking agent for the component(A1).

The crosslinking polyvinyl ether compound as the component (C1) has thefollowing action. That is, the component (C1) functions as follows withthe component (A1).

When a three-component chemical amplification type positive photoresistcomposition is applied on a substrate and then prebaked at a temperaturewithin a range from 80 to 150° C., and preferably 120° C. or higher, thecrosslinking reaction between the components (C1) and (A1) is caused byheating to form a resist layer, which is insoluble or slightly solublein alkali, over the entire surface of the substrate. In the exposurestep and the PEB step, crosslinking is decomposed by an action of anacid generated from the component (B1), and thus the exposed areabecomes alkali soluble and the unexposed area remains alkali insoluble.Therefore, the exposed area can be removed by alkali development to forma resist pattern.

Therefore, the component (C1) is not specifically limited as long as ithas such a function.

As the component (C1), for example, a compound having at least twocrosslinking vinyl ether groups can be used. Specific examples thereofinclude ethylene glycol divinyl ether, triethylene glycol divinyl ether,1,3-butanediol divinyl ether, tetramethylene glycol divinyl ether,neopentyl glycol divinyl ether, trimethylolpropanetrivinyl ether,trimethylolethane trivinyl ether, hexanediol divinyl ether,1,4-cyclohexanediol divinyl ether, tetraethylene glycol divinyl ether,pentaerythritol divinyl ether, pentaerythritol trivinyl ether andcyclohexane dimethanol divinyl ether. Among these compounds, acrosslinking divinyl ether compound is more preferable.

Also the divinyl ether compound is preferably a compound represented bythe following general formula (III′):H₂C═CH—O—R¹² —O—CH═CH₂   (III′)

In the general formula (III′), R¹² is a branched or linear alkylenegroup having 1 to 10 carbon atoms which may have a substituent, or asubstituent represented by the following general formula (IV′). Thealkylene group may have an oxygen bond (ether bond) in the main chain.

In the general formula (IV′), R¹³ is also a branched or linear alkylenegroup having 1 to 10 carbon atoms which may have a substituent, and thealkylene group may have an oxygen bond (ether bond) in the main chain.

Y is 0 or 1.

R¹² is preferably —C₄H₈—, —C₂H₄OC₂H₄—, —C₂H₄OC₂H₄—, or a substituentrepresented by the general formula (IV′). Among these, a substituentrepresented by the general formula (IV′) is preferable. The compound ispreferably a compound wherein R¹³ has one carbon atom and Y is 1(cyclohexane dimethanol divinyl ether).

As the component (C1), one or more kinds can be used in combination.

(B1) Compound Generating an Acid Under Irradiation With Radiation

In this aspect, the positive photoresist composition may furthercontain, as the component (B1), conventionally known photo acidgenerators used in a conventional chemical amplification typephotoresist composition. As the photo acid generator, there havehitherto been known various photo acid generators, for example, oniumsalts such as iodonium salt and sulfonium salt, oxime sulfonates,bisalkyl or bisarylsulfonylazomethanes, poly(bissulfonyl)diazomethanes,diazomethanenitrobenzyl sulfonates, iminosulfonates and disulfones, andtherefore, the component (B1) is not specifically limited and isselected from these conventionally known photo acid generators.

Specific examples of diazomethane photo acid generators includebis(isopropylsulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane andbis(2,4-dimethylphenylsulfonyl)diazomethane.

Specific examples of oxime sulfonate photo acid generators includeα-(methylsulfonyloxyimino)-phenylacetonitrile,α-(methylsulfonyloxyimino)-p-methoxyphenylacetonitrile,α-(trifluoromethylsulfonyloxyimino)-phenylacetonitrile,α-(trifluoromethylsulfonyloxyimino)-p-methoxyphenylacetonitrile,α-(ethylsulfonyloxyimino)-p-methoxyphenylacetonitrile,α-(propylsulfonyloxyimino)-p-methylphenylacetonitrile andα-(methylsulfonyloxyimino)-p-bromophenylacetonitrile. Among these,α-(methylsulfonyloxyimino)-p-methoxyphenylacetonitrile is preferable.

Specific examples of onium salt photo acid generators includetrifluoromethane sulfonate or nonafluorobutane sulfonate ofdiphenyliodonium, trifluoromethane sulfonate or nonafluorobutanesulfonate of bis(4-tert-butylphenyl)iodonium, trifluoromethane sulfonateof triphenylsulfonium, heptafluoropropane sulfonate thereof ornonafluorobutane sulfonate thereof, trifluoromethane sulfonate oftri(4-methylphenyl)sulfonium, heptafluoropropane sulfonate ornonafluorobutane sulfonate thereof, trifluoromethane sulfonate ofdimethyl(4-hydroxynaphthyl)sulfonium, heptafluoropropane sulfonate ornonafluorobutane sulfonate thereof, trifluoromethane sulfonate ofmonophenyldimethylsulfonium, heptafluoropropane sulfonate thereof ornonafluorobutane sulfonate thereof, trifluoromethane sulfonate ofdiphenylmonomethylsulfonium, and heptafluoropropane sulfonate ornonafluorobutane sulfonate thereof.

Examples of poly(bissulfonyl)diazomethane photo acid generators include1,3-bis(phenylsulfonyldiazomethylsulfonyl)propane (compound A,decomposition point: 135° C.),1,4-bis(phenylsulfonyldiazomethylsulfonyl)butane (compound B,decomposition point: 147° C.),1,6-bis(phenylsulfonyldiazomethylsulfonyl)hexane (compound C, meltingpoint: 132° C., decomposition point: 145° C.),1,10-bis(phenylsulfonyldiazomethylsulfonyl)decane (compound D,decomposition point: 147° C.),1,2-bis(cyclohexylsulfonyldiazomethylsulfonyl)ethane (compound E,decomposition point: 149° C.),1,3-bis(cyclohexylsulfonyldiazomethylsulfonyl)propane (compound F,decomposition point: 153° C.),1,6-bis(cyclohexylsulfonyldiazomethylsulfonyl)hexane (compound G,melting point: 109° C., decomposition point: 122° C.) and1,10-bis(cyclohexylsulfonyldiazomethylsulfonyl)decane (compound H,decomposition point: 116° C.), each having the following structures.

Among these photo acid generators, photo acid generators (compoundshaving a decomposition point of 120° C. or higher, and preferably from120° C. to 160° C.) are preferable and poly(bissulfonyl)diazomethanephoto acid generators are particularly preferable, and a compound G ismost preferable.

When the photo acid generator having a decomposition point of 120° C. orhigher, neither decomposition nor sublimation occurs in the case ofprebaking or post exposure baking.

In the second aspect, prebaking can be conducted at low temperature upto about 80° C. and the range of selection of prebaking is widened,preferably.

Therefore, the component (B1) is not limited topoly(bissulfonyl)diazomethane photo acid generators having excellentheat resistance and the range of selection of the photo acid generatoris widened, preferably. Among these, bisalkyl orbisarylsulfonylazomethanesa are preferable because of excellentresolution.

The content of the component (B1) is adjusted within a range from 0.5 to30 parts by weight, and preferably 1 to 10 parts by weight, based on 100parts by weight of the component (A1). When the content is less than theabove range, sufficient pattern formation may not occur. On the otherhand, when the content exceeds the above range, a uniform solution maynot be obtained and storage stability may deteriorate.

As the component (B1), one or more kinds can be used in combination.

(D′) Nitrogen-Containing Organic Compound

The positive resist composition of this aspect can further contain, asan optional component, a nitrogen-containing organic compound (D′)(hereinafter referred to as a component (D′)) so as to improve resistpattern shape and storage stability over time.

Since various compounds have already been proposed, the component (D′)may be any compound selected from conventionally known compounds and ispreferably an amine, and particularly preferably a secondary loweraliphatic amine or tertiary lower aliphatic amine.

As used herein, the lower aliphatic amine refers to an amine of an alkylor alkyl alcohol having 5 or fewer carbon atoms. Examples of thesecondary and tertiary amines include trimethylamine, diethylamine,triethylamine, di-n-propylamine, tri-n-propylamine, tripentylamine,diethanolamine, and triethanolamine. Among these amines, a tertiaryalkanolamine such as triethanolamine is preferable.

These amines may be used alone or in combination.

The component (D′) is commonly used in an amount within a range from0.01 to 5.0 parts by weight based on 100 parts by weight of thecomponent (A1).

Component (E)

The positive photoresist composition of this aspect can further contain,as an optional component, an organic carboxylic acid or oxo acid ofphosphorus or its derivative (E) (hereinafter referred to as a component(E)) so as to prevent deterioration of sensitivity due to the use incombination with the component (D′) and to improve resist pattern shapeand storage stability. The component (D′) can be used in combinationwith the component (E) and either of them can also be used.

As the organic carboxylic acid, for example, malonic acid, citric acid,malic acid, succinic acid, benzoic acid, and salicyclic acid arepreferable.

Examples of the oxo acid of phosphorus or derivatives thereof includephosphoric acid or derivatives thereof such as ester, for example,phosphoric acid, di-n-butyl phosphate or diphenyl phosphate; phosphonicacid or derivatives thereof such as ester, for example, phosphonic acid,dimethylester phosphonate or di-n-butyl phosphonate, phenyl phosphonicacid, diphenyl phosphonate, dibenzyl phosphonate; and phosphinic acid orderivatives thereof such as ester, for example, phosphinic acid,phenylphosphinic acid. Among these, phosphonic acid is particularlypreferable.

The content of the component (E) is from 0.01 to 5.0 parts by weightbased on 100 parts by weight of the component (A1).

Organic Solvent

The positive resist composition of this aspect can be prepared bydissolving materials in an organic solvent.

The organic solvent is not specifically limited as long as it candissolve the respective components used to give a uniform solution, andone or more kinds can be appropriately selected from those which areconventionally known as solvents for a chemical amplification typeresist.

Examples thereof include ketones such as γ-butyrolactone, acetone,methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone and2-heptanone; polyhydric alcohols and their derivatives, such as ethyleneglycol, ethylene glycol monoacetate, diethylene glycol, diethyleneglycol monoacetate, propylene glycol, propylene glycol monoacetate,dipropylene glycol, and monomethyl ether, monoethyl ether, monopropylether, monobutyl ether and monophenyl ether of dipropylene glycolmonoacetate; cyclic ethers such as dioxane; and esters such as methyllactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butylacetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate andethyl ethoxypropionate.

These organic solvents may be used alone or in combination.

A solvent mixture of propylene glycol monomethyl ether acetate (PGMEA)and a polar solvent is preferable. The mixing ratio (weight ratio) maybe appropriately decided taking account of compatibility of PGMEA withthe polar solvent, and is preferably within a range from 1:9 to 8:2, andmore preferably from 2:8 to 5:5.

More specifically, the weight ratio of PGMEA to EL is preferably from2:8 to 5:5, and more preferably from 3:7 to 4:6, in the case of using ELas the polar solvent.

In addition, a solvent mixture of at least one selected from PGMEA andEL, and γ-butyrolactone is also preferable as the organic solvent. Inthis case, the mixing ratio of the former to the latter is preferablyfrom 70:30 to 95:5 in terms of a weight ratio.

The amount of the organic solvent is not specifically limited and isappropriately adjusted so as to be applied on a substrate afterpreparing a coating solution having a predetermined concentration,according to the thickness of the coating film. The content of theorganic solvent is commonly within a range from 2 to 20% by weight, andpreferably from 5 to 15% by weight, based on the solid content of theresist composition.

Other Optional Components

If necessary, the positive resist composition of this aspect may furthercontain miscible additives, for example, additive resins used forimproving performances of the resist film, surfactants used forimproving coatability, dissolution inhibitors, plasticizers,stabilizers, colorants and antihalation agents.

Method For Formation of Resist Pattern

The resist pattern forming method of this aspect can be conducted in thefollowing manner.

First, the above positive resist composition is applied on a substratesuch as silicon wafer using a spinner and is then prebaked (PB) underthe temperature conditions, for example, at 80° C. or higher, preferably120° C. or higher and 150° C. or lower, for 40 to 120 seconds,preferably 60 to 90 seconds. After selectively exposing to KrF excimerlaser beam via a desired mask pattern using a KrF stepper, PEB (postexposure bake) is conducted under temperature conditions of, forexample, 80 to 150° C., for 40 to 120 seconds, and preferably 60 to 90seconds.

In view of formation of the crosslinked structure, prebaking ispreferably conducted under temperature conditions of, for example, 80°C. or higher, and preferably 90 to 110° C.

Then, development treatment is conducted using an alkali developersolution, for example, an aqueous 0.1-10 wt % TMAH solution. Thus aresist pattern, which is faithful to the mask pattern, can be obtained.

Between the substrate and the coating layer made of the resistcomposition, an organic or inorganic antireflective coat can also beprovided.

The wavelength of light used for exposure is not specifically limitedand the exposure can be conducted using radiation such as ArF excimerlaser, KrF excimer laser, F₂ excimer laser, EUV (extreme ultravioletlight), VUV (vacuum ultraviolet light), EB (electron beam), X-rays andsoft X-rays. A KrF excimer laser is particularly effective for thechemical amplification type positive photoresist composition of thisaspect.

In the chemical amplification type positive photoresist composition andthe method for formation of a resist pattern according to the secondaspect of the present invention, excellent resolution can be obtained.When using a short-wavelength light source such as a KrF excimer laser,required fine patterns can be resolved. More specifically, in the caseof L&S (line-and-space) pattern, it is made possible to resolve apattern having a width of about 300 nm or less, preferably. Furthermore,reduction in defects can be realized. Therefore, failure of finepatterns can be avoided and it is very advantageous for highintegration.

In this example, the reason why excellent resolution is obtained is notcertain, but one factor is believed to be as follows. That is, since thecomponent (A1) has a small dissolution rate, a difference in solubilitybetween the unexposed area and the exposed area increases.

One factor for reduction in defects is believed to be as follows. Thatis, since it is not necessary to protect the component (A1) with an aciddissociable dissolution inhibiting group, it is less likely to causesuch a failure that the substance involved in defects dissolved in analkali developer solution is deposited when rinsed with pure water afterdeveloping with an alkali developer solution.

Also line edge roughness (LER: unevenness of line side wall) can besuppressed. It is believed that reduction in LER is caused by the samefactors as in the case of defects.

In the formation of the resist pattern, since the unexposed area iscomposed of a coating film containing a base resin having comparativelyhigh molecular weight wherein a crosslinked structure is formed of thecomponent (C1), there is also exerted the effect that the resist patternhas excellent heat resistance.

Also the acid component generated from the component (B1) exerts theeffect capable of raising the limit for PEB conditions becauseconversion of slight alkali solubility or alkali insolubility intoalkali solubility due to the acid component requires a relatively smallamount of energy.

EXAMPLES Example of First Aspect

In this example, various physical properties of a photoresistcomposition were determined in the following manner. A basic operationof forming a resist pattern is as follows.

Using a spinner, the photoresist composition was applied on a siliconwafer and then dried on a hot plate at 130° C. for 90 seconds to form aresist film having a thickness of 3 μm. This film was selectivelyexposed via a mask using a Step-and-Repeat System NSR-2005i10D(manufactured by Nikon Corporation, NA (Numerical Aperture)=0.57(variable)), subjected to a PEB (post exposure bake) treatment at 110°C. for 90 seconds, developed with an aqueous 2.38 wt % TMAH solution at23° C. for 60 seconds, washed with water for 30 seconds, and then dried.

(1) Eop Sensitivity

The exposure time required to form a pattern composed of line-and-spacewidth (L&S) (1:1) each having a width of 1.5 μm by selective exposure atintervals within a range from 0.1 to 0.01 seconds is represented as Eopsensitivity in units of milliseconds (ms).

Eop sensitivity of 400 ms is suited as a thick film used for formationof implantation or metal wiring.

(2) Resolution

Resolution was represented by threshold resolution at the Eopsensitivity (Eop exposure amount).

(3-1) Profile (Evaluation of Pattern Dependence: Fine Pattern):

A profile of a resist pattern composed of L&S (1:1) each having a widthof 1.5 μm was observed by SEM (scanning electron microscope) micrograph.The case in which a rectangular profile was obtained was rated “A”, thecase in which a generally rectangular profile was observed, however,T-top shape, undercutting shape at the substrate interface or tailingshape was observed was rated “B”, and the case where separated patterncould not be obtained was rated “C”.

(3-2) Profile (Evaluation of Pattern Dependence: Rough Pattern):

A profile of a resist pattern composed of L&S (1:1) each having a widthof 5.0 μm was observed in a SEM (scanning electron microscope)micrograph. The case where a rectangular profile was obtained was rated“A”, the case where generally rectangular profile was observed, however,T-top shape, undercutting shape at the substrate interface or tailingshape was observed was rated “B”, and the case where separated patterncould not be obtained was rated “C”.

(4) Evaluation of Storage Stability as Resist Solution in Bottle

The resist composition was prepared and, after sampling in a bottle, itwas stored at room temperature (25° C.) and exposure amount dimensionalcurve was measured. As a result, the case where no dimensional changewas observed after 3 months was rated “A”, and the case wheredimensional change was observed after 2 weeks was rated “B”.

The exposure amount dimensional curve was determined as follows. Thatis, the resist composition was periodically sampled during storage andselective exposure at the resist sensitivity (above Eop sensitivity)before storage was conducted. The dimensional width (line width) of theresulting 1.5 μm L&S was measured by critical dimension measurement SEMand the resulting values were plotted.

(5) Evaluation of Heat Resistance

After development, postbaking was conducted under conditions at 110° C.,120° C., 130° C., 140° C., 150° C. and 160° C. for 300 seconds and aprofile of a 5.0 μm pattern was observed by a SEM (scanning electronmicroscope).

As a result, maximum temperature at which a pattern shape did notsubstantially change is shown in the table.

When the resulting pattern has good rectangular shape even at 150° C.,it is suited as a thick film used for implantation or metal wiring.

In this example, a thick-film process such as implantation and metalwiring was not actually conducted. However, it can be judged whether ornot it is suited for such applications by evaluation of sensitivity andheat resistance.

Synthesis Example 1 Synthesis of Novolak Resin 1

Using a phenol mixture of m-cresol/p-cresol in a molar ratio of 40/60and an aldehyde mixture of formaldehyde/salicylaldehyde in a molar ratioof 1/0.3, the condensation polymerization reaction was conducted by aconventional method to obtain a novolak resin. The resulting novolakresin has Mw of 5449 and a dispersion degree (Mw/Mn) of 10.4 (Mn:weight-average molecular weight).

The concentration 10 ppm of the acid component in the novolak resin wasreduced to 10 ppm or less by the following treatment. After thetreatment, the concentration of the acid component was lower than 0.1ppm as a detection limit.

100 g of the novolak resin was dissolved in MIBK (methyl isobutylketone) to obtain a solution having a solid content of 30% by weight andthe same amount as that of the solution of pure water was added to thesolution, followed by stirring for 15 minutes. After the completion ofstirring, the reaction solution was allowed to stand and the separatedpure water layer was removed. Using pure water, the same operation wasrepeated six times. Then, the solution was concentrated under reducedpressure until the water content in the solution was reduced to 0.1% byweight to obtain a novolak resin solution wherein the acid component isremoved.

Synthesis Example 2 Synthesis of Novolak Resin 2

Using m-cresol and formaldehyde, the condensation polymerizationreaction was conducted by a conventional method to obtain a novolakresin. The resulting novolak resin had a Mw of 8137 and a dispersiondegree (Mw/Mn) of 11.5.

Then, the concentration 10 ppm of the acid component in the novolakresin was reduced to 10 ppm or less by the same treatment as inSynthesis Example 1. After the treatment, the concentration of the acidcomponent was lower than 0.1 ppm which is a detection limit.

Synthesis Example 3 Synthesis of Novolak Resin 3

Using m-cresol and an aldehyde mixture of formaldehyde/salicylaldehydein a molar ratio of 1/0.3, the condensation polymerization reaction wasconducted by a conventional method to obtain a novolak resin. Theresulting novolak resin had a Mw of 5718 and a dispersion degree (Mw/Mn)of 8.0.

Then, the concentration 10 ppm of the acid component in the novolakresin was reduced to 10 ppm or less by the same treatment as inSynthesis Example 1. After the treatment, the concentration of the acidcomponent was lower than 0.1 ppm which is a detection limit.

Synthesis Example 4 Synthesis of Preresin 1

While stirring, the novolak resin 1 was dissolved in a methyl isobutylketone (MIBK) solvent at a concentration of 30% by weight and, aftercontrolling the inner temperature within a range from 100 to 110° C., acrosslinking agent (cyclohexane dimethanol divinyl ether) was addeddropwise in the amount of 8 parts by weight based on 100 parts by weightof the solid content of the resin.

During the dropwise addition, the concentration of the crosslinkingagent was controlled to 30% by weight (in a MIBK solution). Afterreacting for 24 hours, post-stirring was conducted at room temperaturefor 12 hours or more, the solvent MIBK was replaced by 2-heptanone.

The resulting component (A) (preresin 1) had a weight-average molecularweight of 25000.

The concentration of the acid component in the component (A) was 2.5ppm.

Synthesis Example 5 Synthesis of Preresin 2

In the same manner as in Synthesis Example 4, except that the novolakresin 2 was used, a preresin 2 was obtained. The weight-averagemolecular weight was 38000 and the concentration of the acid componentwas 2.2 ppm.

Synthesis Example 6 Synthesis of Preresin 3

In the same manner as in Synthesis Example 4, except that novolak resin3 was used, a preresin 3 was obtained. The weight-average molecularweight was 23000 and the concentration of the acid component was 1.8ppm.

Synthesis Example 7 Synthesis of Preresin 4

A styrenic resin 1 (hydroxystyrene-styrene copolymer (content of styreneconstituent unit: 10 mol %, weight-average molecular weight: 2500)) waspurified by ion exchange and, after replacing by γ-butyrolactone, theconcentration was adjusted to 30% by weight. Then, acetic acid was addedin a proportion of 0.1% based on the solid content of the resin and acrosslinking agent (cyclohexane dimethanol divinyl ether) was addeddropwise in an amount of 9.5 parts by weight based on 100 parts byweight of the solid content of the resin while stirring at an innertemperature within a range from 100 to 110° C.

During the dropwise addition, the concentration of the crosslinkingagent was adjusted to 30% by weight (in a γ-butyrolactone solution).After reacting for 21 hours, 4 g of pyridine was added dropwise. Afterstirring for one hour at room temperature, the solution was dissolved in2-heptanone. The resulting solution was washed five times withmethanol/pure water, and then the 2-heptanone layer was separated andconcentrated to remove the residual methanol/water.

The resulting component (A′) and a weight-average molecular weight of85563. The concentration of the acid component was 0.51 ppm.

Synthesis Example 8 Synthesis of Preresin 5

In the same manner as in Synthesis Example 7, except that a styrenicresin 2 (hydroxystyrene-styrene copolymer (content of styreneconstituent unit: 5 mol %, weight-average molecular weight: 4000)) wasused, a component (A′) (weight-average molecular weight: 96500,concentration of acid component: 0.8 ppm) was prepared.

Synthesis Example 9 Synthesis of Preresin 6

In the same manner as in Synthesis Example 7, except that a styrenicresin 3 (hydroxystyrene-styrene copolymer (content of styreneconstituent unit: 20 mol %, weight-average molecular weight: 2000)) wasused, a component (A′) (weight-average molecular weight: 65000,concentration of acid component: 1.5 ppm) was prepared.

Synthesis Example 10 Synthesis of Preresin 7

In the same manner as in Synthesis Example 7, except that a styrenicresin 4 (polyhydroxystyrene (weight-average molecular weight: 4000)) wasused, a component (A′) (weight-average molecular weight: 87000,concentration of acid component: 2.5 ppm) was prepared.

Example 1

Component (A) (preresin 1): 100 parts by weight (calculated based on thesolid content)

Component (B) (compound represented by the general formula (vii)): 2parts by weight

Component (C) (t-n-decylamine): 0.2 parts by weight

Other components (2,6-di(tert-butyl)-p-cresol): 0.5 parts by weight

The above components were dissolved in 2-heptanone in a concentration of35% by weight and then filtered through a membrane filter having a porediameter of 0.2 μm to prepare a resist composition. Physical properties(1) to (5) and the concentration of the acid component (acid componentmeasured: oxalic acid, propionic acid, formic acid and acetic acid, thesame rule applies to the following) of the resist composition are shownin Table 1.

Examples 2 to 7

In the same manner as in Example 1, except that the component (A) wasreplaced by the preresins 2 to 7 (each corresponding to Examples 2 to 7)synthesized in the above Synthesis Examples in Example 1, resistcompositions were prepared.

Physical properties (1) to (5) and the concentration of the acidcomponent of these resist compositions are shown in Table 1.

Comparative Example 1

In the same manner as in Example 1, except that acetic acid was added tothe resist composition used in Example 1 and the concentration of theacid component of the resist composition was adjusted to 24.9 ppm inExample 1, a resist composition was prepared.

Physical properties (1) to (5) and the concentration of the acidcomponent of this resist composition are shown in Table 1.

Comparative Example 2

Component (A) (novolak resin 1): 100 parts by weight (calculated basedon the solid content)

Component (B) (compound represented by the general formula (vii)): 2parts by weight

Component (C) (t-n-decylamine): 0.2 parts by weight

Other components (cyclohexane dimethanol divinyl ether): 8 parts byweight

The above components were dissolved in 2-heptanone in the concentrationof 35% by weight and then filtered through a membrane filter having apore diameter of 0.2 μm to prepare a resist composition.

Physical properties (1) to (5) and the concentration of the acidcomponent of the resist composition are shown in Table 1.

Comparative Examples 3 to 8

In the same manner as in Examples 2 to 7, except that acetic acid wasadded to the resist composition used in Examples 2 to 7 and theconcentration of the acid component of the resist composition wasadjusted to the concentration shown in Table 1, resist compositions wereprepared.

Physical properties (1) to (5) and the concentration of the acidcomponent of the resist compositions are shown in Table 1.

Comparative Example 9

In the same manner as in Example 1, except that a novolak-naphthoquinonepositive photoresist composition for i-ray “THMR-iP5800” (trade name:manufactured by Tokyo Ohka Kogyo Co., Ltd.) was used in place of thecomposition of Example 1, a resist compositions was prepared. Physicalproperties (1) to (5) of the resist composition are shown in Table 1.TABLE 1 (3-2) (1) (2) (3-1) Profile (4) (5) Concentration of Eopsensitivity Resolution Profile (fine (rough Storage stability as a Heatresistance Acid component (ms) (μm) pattern) pattern) resist solution ina bottle (° C.) (ppm) Example 1 320 0.7 A A A 160 0.4 Example 2 380 0.7B B A 120 0.3 Example 3 260 0.7 B A A 140 0.3 Example 4 140 0.8 A A A150 0.3 Example 5 200 0.8 B B A 150 0.1 Example 6 180 0.8 B B A 140 0.4Example 7 180 0.8 B B A 140 0.8 Comparative 320 0.7 A A B 160 24.9Example 1 Comparative 420 0.6 B B B 160 4.2 Example 2 Comparative 3800.7 B B B 120 35.2 Example 3 Comparative 260 0.7 B A B 140 49.5 Example4 Comparative 140 0.6 A A B 150 19.8 Example 5 Comparative 200 0.8 B B B150 33.7 Example 6 Comparative 180 0.8 B B B 140 13.9 Example 7Comparative 180 0.8 B B B 140 21.2 Example 8 Comparative 450 0.7 C B A120 not measured Example 9

As is apparent from the results shown in Table 1, the resist compositionof this aspect was excellent in sensitivity, resolution, and storagestability as a resist solution in a bottle, and also exhibited goodprofile in both cases of a rough pattern and a fine pattern and wasexcellent in heat resistance.

Examples of Second Aspect Synthesis Examples

A resin 1 and a resin 2 were synthesized in the following manner.

Synthesis of Resin 1

In the same manner as in Synthesis Example 7, except that a copolymer(weight-average molecular weight: 3000; corresponding to the component(A1)) obtained by polymerizing 70 mol % of a monomer (p-hydroxystyrene)capable of deriving a constituent unit (a1′) of the general formula (I′)wherein R=hydrogen atom, 1=1 and hydroxyl group is linked at thep-position with 30 mol % of a monomer (styrene) capable of deriving aconstituent unit (a2′) of the general formula (II′) wherein R=hydrogenatom and p=0 was used in place of the styrenic resin 1 in SynthesisExample 7, a resin 1 was synthesized. The weight-average molecularweight was 45000.

Synthesis of Resin 2

In the same manner as in the case of the synthesis of the resin 1,except that a copolymer (weight-average molecular weight: 2500)comprising the monomer (p-hydroxystyrene) capable of deriving theconstituent unit (a1′) and the monomer (styrene) capable of deriving theconstituent unit (a2′) in a ratio of 90 mol %: 10 mol % was used inplace of the copolymer synthesized in the Synthesis Example in thesynthesis of the resin 1, a resin 2 was obtained. The weight-averagemolecular weight was 86000.

Example 8

The following materials were dissolved in the following organic solventto prepare a chemical amplification type positive photoresistcomposition.

Component (A2) (resin mixture of resin 1/resin 2 in a weight ratio of1:1): 100 parts by weight

Component (B2) (compound represented by the following chemical formula):5 parts by weight

Component (D′) (triethanolamine): 0.15 parts by weight

Organic solvent (PGMEA/EL=6/4(weight ratio)): 630 parts by weight

Comparative Example 10

Resin Component: 100 Parts by Weight

(Mixture of 75 parts by weight of a resin obtained by protecting 39 mol% of hydroxyl groups of a hydroxystyrenic resin (homopolymer ofp-hydroxystyrene, weight-average molecular weight: 12000, dispersiondegree=2.2) comprising only a constituent unit (a1′) of the generalformula (I′) wherein R=hydrogen atom, 1=1 and hydroxyl group is linkedat the p-position, with a 1-ethoxyethyl group, and 25 parts by weight ofa resin obtained by protecting 35 mol % of hydroxyl groups of ahydroxystyrenic resin (homopolymer of p-hydroxystyrene, weight-averagemolecular weight: 12000, dispersion degree=2.2) comprising only aconstituent unit (a1′) of the general formula (I′) wherein R=hydrogenatom, 1=1 and a hydroxyl group is linked at the p-position, with a t-bocgroup, dissolution rate: 0.5 nm/second

Component (B1) (bis(cyclohexylsulfonyl)diazomethane): 5.0 parts byweight

Component (D′) (triethanolamine) 0.1 parts by weight

Organic solvent (PGMEA): 600 parts by weight

Comparative Example 11

Component (A1): hydroxystyrenic resin (resin comprising only aconstituent unit (a1′) of the general formula (I′) wherein R=hydrogenatom, 1=1 and a hydroxyl group is linked at the p-position) (homopolymerof p-hydroxystyrene, weight-average molecular weight: 12000, dispersiondegree: 2.2): 100 parts by weight

Dissolution rate: 500 nm/second or more

Component (B1): the same as in Comparative Example 10

Component (C1): cyclohexane dimethanol divinyl ether 20 parts by weight

Component (D′): the same as in Comparative Example 10

Organic solvent PGMEA/EL=6/4(weight ratio): 630 parts by weight

Evaluation Method

With respect to the chemical amplification type positive photoresistcompositions obtained in Example 8 and Comparative Examples 10 and 11,the following evaluations (1) to (2) were conducted.

(1) Evaluation of Resolution

Each resist composition was applied on an 8-inch Si substrate whosesurface was treated with hexamethyldisilazane (HMDS) using a spinner andwas then dried on a hot plate by prebaking under the conditions at 130°C. for 60 seconds (Example 8), at 100° C. for 60 seconds (ComparativeExample 10) or at 130° C. for 60 seconds (Comparative Example 11) toobtain a resist film having a thickness of 540 nm (Example 8) and resistfilms having a thickness of 420 nm (Comparative Examples 10 and 11).

Using a KrF aligner (trade name: “NSR-S203B”, manufactured by NikonCorporation, NA=0.60, σ=0.65), the resist film was selectivelyirradiated (selective exposure) with KrF excimer laser (248 nm) via amask (binary), subjected to a PEB treatment under conditions at 110° C.for 60 seconds (Example 8), at 110° C. for 60 seconds (ComparativeExample 10) or at 130° C. for 60 seconds (Comparative Example 11),puddle-developed with an aqueous 2.38 wt % tetramethylammonium hydroxidesolution at 23° C. for 60 seconds and then rinsed with pure water for 10seconds. After subjecting to shake-off drying and drying, a L&S(line-and-space) pattern was formed.

Then, the exposure amount (EOP₃₀₀, unit: mJ/cm²) at which a L&S resistpattern having a line width 300 nm and a pitch of 600 nm can befaithfully reproduced was determined.

Selective exposure was conducted at the above EOP₃₀₀ and the formedpattern was observed by a scanning electron microscope.

As a result, a L&S pattern of 180 nm (pitch: 360 nm) could be resolvedin Example 8, while only a L&S pattern of 220 nm (pitch: 440 nm) couldbe resolved in Comparative Example 10. The entire resist film wasdissolved during the development in Comparative Example 11.

With respect to the Examples, the same test was conducted by varying thetemperature of prebaking and PEB. As a result, a L&S pattern of 180 nm(pitch: 360 nm) could be resolved at the prebake temperature/PEBtemperature of 120° C./110° C., 130° C./100° C. and 130° C./110° C.

(2) Evaluation of Defects

With respect to the resist pattern formed in the above evaluation (1),defects were measured by a surface defect detection equipment KLA2132(trade name) manufactured by KLA-TENCOR CORPORATION and then the numberof defects on the wafer was evaluated.

As a result, the number of defects per wafer was 5 in Example 8, and 260in Comparative Example 10. In Comparative Example 11, evaluation couldnot be conducted because the entire resist film was dissolved.

It could be confirmed from the evaluation results of the above Examplesand Comparative Examples that the chemical amplification type positivephotoresist composition of this aspect exerts the effect of improvingresolution and reducing defects.

INDUSTRIAL APPLICABILITY

The chemical amplification type positive photoresist composition and theresist pattern forming method of the present invention are suited foruse in the fields of the production of semiconductors and liquid crystaldevices.

1. A chemical amplification type positive photoresist compositionprepared by dissolving: (A′) an slightly alkali-soluble oralkali-insoluble polyhydroxystyrenic resin having a property thatsolubility in an aqueous alkali solution is enhanced in the presence ofan acid, comprising either or both of a constituent unit (a′1)represented by the following general formula

(IV): wherein R¹ represents either an alkylene group having 1 to 10carbon atoms which may have a substituent or a group represented by thefollowing general formula (II)

(wherein R⁴ represents an alkylene group having 1 to 10 carbon atomswhich may have a substituent and m represents 0 or 1), the alkylenegroup may have an oxygen bond (ether bond) in the main chain, and anintermolecular crosslinked moiety (a′2) represented by the followinggeneral formula (V):

wherein R¹ represents either an alkylene group having 1 to 10 carbonatoms which may have a substituent or a group represented by the abovegeneral formula (II) (wherein R⁴ represents an alkylene group having 1to 10 carbon atoms which may have a substituent and m represents 0 or1), the alkylene group may have an oxygen bond (ether bond) in the mainchain; and (B) a compound generating an acid under irradiation withradiation, in an organic solvent, wherein said organic solvent is anon-ester solvent, and the content of an acid component in thephotoresist composition is 10 ppm or less.
 2. The chemical amplificationtype positive photoresist composition according to claim 1, wherein thecomposition further comprises a storage stabilizer.
 3. The chemicalamplification type positive photoresist composition according to claim2, wherein the storage stabilizer is an antioxidant.
 4. The chemicalamplification type positive photoresist composition according to claim1, wherein the component (B) is a compound generating an acid underirradiation with i-rays (365 nm).
 5. The chemical amplification typepositive photoresist composition according to claim 1, which furthercomprises a basic compound as the component (C).
 6. The chemicalamplification type positive photoresist composition according to claim5, which comprises the component (C) in the amount of 0.01 to 5 parts byweight based on 100 parts by weight of the resin component contained inthe resist composition.
 7. The chemical amplification type positivephotoresist composition according to claim 1, which comprisesγ-butyrolactone in the amount of from 1 to 10 parts by weight based onthe solid content of the resist composition.
 8. The chemicalamplification type positive photoresist composition according to claim1, which is used for a thick-film photolithography process used forforming a resist film having a thickness of about 2 to 7 μm.
 9. Thechemical amplification type positive photoresist composition accordingto claim 8, wherein the thick-film photolithography process is used forforming a resist pattern for implantation.
 10. A chemical amplificationtype positive photoresist composition prepared by dissolving: (A′) anslightly alkali-soluble or alkali-insoluble polyhydroxystyrenic resinhaving a property that solubility in an aqueous alkali solution isenhanced in the presence of an acid, comprising either or both of aconstituent unit (a′1) represented by the following general formula

(IV): wherein R¹ represents either an alkylene group having 1 to 10carbon atoms which may have a substituent or a group represented by thefollowing general formula (II)

(wherein R⁴ represents an alkylene group having 1 to 10 carbon atomswhich may have a substituent and m represents 0 or 1), the alkylenegroup may have an oxygen bond (ether bond) in the main chain, and anintermolecular crosslinked moiety (a′2) represented by the followinggeneral formula (V):

wherein R¹ represents either an alkylene group having 1 to 10 carbonatoms which may have a substituent or a group represented by the abovegeneral formula (II) (wherein R⁴ represents an alkylene group having 1to 10 carbon atoms which may have a substituent and m represents 0 or1), the alkylene group may have an oxygen bond (ether bond) in the mainchain; and (B) a compound generating an acid under irradiation withradiation, in an organic solvent, wherein said organic solvent is anester solvent and the content of an acid component is 10 ppm or less.11. The chemical amplification type positive photoresist compositionaccording to claim 10, wherein the composition further comprises astorage stabilizer.
 12. The chemical amplification type positivephotoresist composition according to claim 11, wherein the storagestabilizer is an antioxicant.
 13. The chemical amplification typepositive photoresist composition according to claim 11, wherein theorganic solvent is propylene glycol monomethyl ether acetate.
 14. Thechemical amplification type positive photoresist composition accordingto claim 10, wherein the component (B) is a compound generating an acidunder irradiation with i-rays (365 nm).
 15. The chemical amplificationtype positive photoresist composition according to claim 10, whichfurther comprises a basic compound as the component (C).
 16. Thechemical amplification type positive photoresist composition accordingto claim 15, which comprises the component (C) in the amount of 0.01 to5 parts by weight based on 100 parts by weight of the resin componentcontained in the resist composition.
 17. The chemical amplification typepositive photoresist composition according to claim 10, which comprisesy-butyrolactone in the amount of from 1 to 10 parts by weight based onthe solid content of the resist composition.
 18. The chemicalamplification type positive photoresist composition according to claim10, which is used for a thick-film photolithography process used forforming a resist film having a thickness of about 2 to 7 μm.
 19. Thechemical amplification type positive photoresist composition accordingto claim 18, wherein the thick-film photolithography process is used forforming a resist pattern for implantation.
 20. A chemical amplificationtype positive photoresist composition prepared by dissolving: (A′) anslightly alkali-soluble or alkali-insoluble polyhydroxystyrenic resinhaving a property that solubility in an aqueous alkali solution isenhanced in the presence of an acid, comprising either or both of aconstituent unit (a′1) represented by the following general formula(IV):

wherein R¹ represents either an alkylene group having 1 to 10 carbonatoms which may have a substituent or a group represented by thefollowing general formula (II)

(wherein R⁴ represents an alkylene group having 1 to 10 carbon atomswhich may have a substituent and m represents 0 or 1), the alkylenegroup may have an oxygen bond (ether bond) in the main chain, and anintermolecular crosslinked moiety (a′2) represented by the followinggeneral formula (V):

wherein R¹represents either an alkylene group having 1 to 10 carbonatoms which may have a substituent or a group represented by the abovegeneral formula (II) (wherein R⁴ represents an alkylene group having 1to 10 carbon atoms which may have a substituent and m represents 0 or1), the alkylene group may have an oxygen bond (ether bond) in the mainchain, and a styrenic constituent unit; and (B) a compound generating anacid under irradiation with radiation, in an organic solvent, whereinsaid organic solvent is a non-ester solvent and the content of an acidcomponent is 10 ppm or less.
 21. The chemical amplification typepositive photoresist composition according to claim 20, wherein thecomposition further comprises a storage stabilizer.
 22. The chemicalamplification type positive photoresist composition according to claim21, wherein the storage stabilizer is an antioxidant.
 23. The chemicalamplification type positive photoresist composition according to claim20, wherein the component (B) is a compound generating an acid underirradiation with i-rays (365 nm).
 24. The chemical amplification typepositive photoresist composition according to claim 20, which furthercomprises a basic compound as the component (C).
 25. The chemicalamplification type positive photoresist composition according to claim24, which comprises the component (C) in the amount of 0.01 to 5 partsby weight based on 100 parts by weight of the resin component containedin the resist composition.
 26. The chemical amplification type positivephotoresist composition according to claim 20, which comprisesy-butyrolactone in the amount of from 1 to 10 parts by weight based onthe solid content of the resist composition.
 27. The chemicalamplification type positive photoresist composition according to claim20, which is used for a thick-film photolithography process used forforming a resist film having a thickness of about 2 to 7 μm.
 28. Thechemical amplification type positive photoresist composition accordingto claim 27, wherein the thick-film photolithography process is used forforming a resist pattern for implantation.
 29. A chemical amplificationtype positive photoresist composition prepared by dissolving: (A′) anslightly alkali-soluble or alkali-insoluble polyhydroxystyrenic resinhaving a property that solubility in an aqueous alkali solution isenhanced in the presence of an acid, comprising either or both of aconstituent unit (a′1) represented by the following general formula(IV):

wherein R¹ represents either an alkylene group having 1 to 10 carbonatoms which may have a substituent or a group represented by the abovegeneral formula (II)

(wherein R⁴ represents an alkylene group having 1 to 10 carbon atomswhich may have a substituent and m represents 0 or 1), the alkylenegroup may have an oxygen bond (ether bond) in the main chain, and anintermolecular crosslinked moiety (a′2) represented by the followinggeneral formula (V):

wherein R¹ represents either an alkylene group having 1 to 10 carbonatoms which may have a substituent or a group represented by the abovegeneral formula (II) (wherein R⁴ represents an alkylene group having 1to 10 carbon atoms which may have a substituent and m represents 0 or1), the alkylene group may have an oxygen bond (ether bond) in the mainchain, and a styrenic constituent unit; and (B) a compound generating anacid under irradiation with radiation, in an organic solvent, whereinsaid organic solvent is an ester solvent and the content of an acidcomponent is 10 ppm or less.
 30. The chemical amplification typepositive photoresist composition according to claim 29, wherein thecomposition further comprises a storage stabilizer.
 31. The chemicalamplification type positive photoresist composition according to claim29, wherein the storage stabilizer is an antioxicant.
 32. The chemicalamplification type positive photoresist composition according to claim30, wherein the organic solvent is propylene glycol monomethyl etheracetate.
 33. The chemical amplification type positive photoresistcomposition according to claim 29, wherein the component (B) is acompound generating an acid under irradiation with i-rays (365 nm). 34.The chemical amplification type positive photoresist compositionaccording to claim 29, which further comprises a basic compound as thecomponent (C).
 35. The chemical amplification type positive photoresistcomposition according to claim 34, which comprises the component (C) inthe amount of 0.01 to 5 parts by weight based on 100 parts by weight ofthe resin component contained in the resist composition.
 36. Thechemical amplification type positive photoresist composition accordingto claim 29, which comprises γ-butyrolactone in the amount of from 1 to10 parts by weight based on the solid content of the resist composition.37. The chemical amplification type positive photoresist compositionaccording to claim 29, which is used for a thick-film photolithographyprocess used for forming a resist film having a thickness of about 2 to7 μm.
 38. The chemical amplification type positive photoresistcomposition according to claim 37, wherein the thick-filmphotolithography process is used for forming a resist pattern forimplantation.
 39. A chemical amplification type positive photoresistcomposition prepared by dissolving: (A′) an slightly alkali-soluble oralkali-insoluble polyhydroxystyrenic resin having a property thatsolubility in an aqueous alkali solution is enhanced in the presence ofan acid, comprising either or both of a constituent unit (a′1)represented by the following general formula (IV):

wherein R¹ represents either an alkylene group having 1 to 10 carbonatoms which may have a substituent or a group represented by thefollowing general formula (II)

(wherein R⁴ represents an alkylene group having 1 to 10 carbon atomswhich may have a substituent and m represents 0 or 1), the alkylenegroup may have an oxygen bond (ether bond) in the main chain, and anintermolecular crosslinked moiety (a′2) represented by the followinggeneral formula (V):

wherein R¹ represents either an alkylene group having 1 to 10 carbonatoms which may have a substituent or a group represented by the abovegeneral formula (II) (wherein R⁴ represents an alkylene group having 1to 10 carbon atoms which may have a substituent and m represents 0 or1), the alkylene group may have an oxygen bond (ether bond) in the mainchain; and (B) a compound generating an acid under irradiation withradiation, in an organic solvent, wherein said compound generating anacid under irradiation with radiation (B) is a compound represented bythe following formula (vi):

wherein Ar represents a substituted or unsubstituted phenyl group or anaphthyl group; R″. represents an alkyl group having 1 to 9 carbonatoms; and n′ represents an integer of 2 or
 3. 40. The chemicalamplification type positive photoresist composition according to claim39, wherein the composition further comprises a storage stabilizer. 41.The chemical amplification type positive photoresist compositionaccording to claim 40, wherein the storage stabilizer is an antioxidant.42. The chemical amplification type positive photoresist compositionaccording to claim 39, which further comprises a basic compound as thecomponent (C).
 43. The chemical amplification type positive photoresistcomposition according to claim 42, which comprises the component (C) inthe amount of 0.01 to 5 parts by weight based on 100 parts by weight ofthe resin component contained in the resist composition.
 44. Thechemical amplification type positive photoresist composition accordingto claim 39, which comprises γ-butyrolactone in the amount of from 1 to10 parts by weight based on the solid content of the resist composition.45. The chemical amplification type positive photoresist compositionaccording to claim 39, which is used for a thick-film photolithographyprocess used for forming a resist film having a thickness of about 2 to7 μm.
 46. The chemical amplification type positive photoresistcomposition according to claim 45, wherein the thick-filmphotolithography process is used for forming a resist pattern forimplantation.